Intermittent MySQL error under high load: "Unknown MySQL server host 'XXXX'"

I have a MySQL server under heavy load (~960 queries per second) with ~ 400 clients continuously running queries against it. It is on a powerful machine (8 cores, Xeon, 3.3 GHz) and it looks like it can keep up with the load, no problem.

Occasionally (once per week), all clie开发者_如何学Cnt processes will error at the same time with the message "Unknown MySQL server 'XXX'". Then, without me doing anything, they all come back to life a short time later.

I have max_connections set to 500, but I think that if I exceed that number then I should get a "Too many connections" error, and not the one I'm seeing.

Can anyone help me figure out why I'm getting these errors?

Thanks,

Jonathan

System specs:
8 cores, Xeon 3.2 GHz
Ubuntu 8.04
Kernel: Linux 2.6.24-27
MySQL 5.0.51a-3ubuntu5.7